diff --git a/src/proto/gui_x11.pro b/src/proto/gui_x11.pro
index 6524c26..035c27f 100644
--- a/src/proto/gui_x11.pro
+++ b/src/proto/gui_x11.pro
@@ -15,6 +15,7 @@
 void gui_mch_get_screen_dimensions __ARGS((int *screen_w, int *screen_h));
 int gui_mch_init_font __ARGS((char_u *font_name, int do_fontset));
 GuiFont gui_mch_get_font __ARGS((char_u *name, int giveErrorIfMissing));
+char_u *gui_mch_get_fontname __ARGS((GuiFont font, char_u *name));
 int gui_mch_adjust_charsize __ARGS((void));
 void gui_mch_set_font __ARGS((GuiFont font));
 void gui_mch_set_fontset __ARGS((GuiFontset fontset));